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1st International Conference on Smart Computing and Communication (SmartCom)

作者： Li, Yang Liu, Duo Zhang, Jingyu Long, Linbo Chongqing Univ Coll Comp Sci Chongqing Peoples R China Chongqing Univ Posts & Telecommun Coll Comp Sci & Technol Chongqing Peoples R China

ISBN: (纸本)9783319520155;9783319520148

Mobile devices are equipped with many hardware accelerators to improve the performance and there are a bunch of third-party applications with rich-features in the application market. However, these applications always request large and contiguous physical memory as IO buffers and we observe that physical memory is severely fragmented after the mobile system runs for several hours. As a result, the memory allocation for such large and contiguous IO buffers will result in high latency and power consumption. Thus, this paper proposes a global memory fragmentation quantification approach that summarizes memory blocks access pattern and measures the allocation time of different order's memory block dynamically. Our evaluation on Android Kitkat shows that the global memory fragmentation is very precise to reflect the fluency of whole system.

关键词： Mobile systems memory fragmentation Quantification Defragmentation Anti-fragmentation

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Controlling Physical memory fragmentation in Mobile Systems 15

Controlling Physical Memory Fragmentation in Mobile Systems

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14th ACM SIGPLAN International Symposium on memory Management (ISMM)

作者： Kim, Sang-Hoon Kwon, Sejun Kim, Jin-Soo Jeong, Jinkyu Korea Adv Inst Sci & Technol Daejeon South Korea Sungkyunkwan Univ Suwon South Korea

ISBN: (纸本)9781450335898

Since the adoption of hardware-accelerated features (e.g., hardware codec) improves the performance and quality of mobile devices, it revives the need for contiguous memory allocation. However, physical memory in mobile systems is highly fragmented due to the frequent spawn and exit of processes and the lack of proactive anti-fragmentation scheme. As a result, the memory allocation for large and contiguous I/O buffers suffers from highly fragmented memory, thereby incurring high CPU usage and power consumption. This paper presents a proactive anti-fragmentation approach that groups pages with the same lifetime, and stores them contiguously in fixed-size contiguous regions. When a process is killed to secure free memory, a set of contiguous regions are freed and subsequent contiguous memory allocations can be easily satisfied without incurring additional overhead. Our prototype implementation on a Nexus 10 tablet with the Android kernel shows that the proposed scheme greatly alleviates fragmentation, thereby reducing the I/O buffer allocation time, associated CPU usage, and energy consumption.

关键词： memory fragmentation Mobile systems

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Controlling Physical memory fragmentation in Mobile Systems

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ACM SIGPLAN NOTICES 2015年第11期50卷 1-14页

作者： Kim, Sang-Hoon Kwon, Sejun Kim, Jin-Soo Jeong, Jinkyu Korea Adv Inst Sci & Technol Daejeon South Korea Sungkyunkwan Univ Suwon South Korea

关键词： memory fragmentation Mobile systems

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PMAlloc: A Holistic Approach to Improving Persistent memory Allocation

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ACM TRANSACTIONS ON COMPUTER SYSTEMS 2024年第3-4期42卷 1-52页

作者： Dang, Zheng He, Shuibing Zhang, Xuechen Hong, Peiyi Li, Zhenxin Chen, Xinyu Song, Haozhe Sun, Xian-he Chen, Gang Zhejiang Univ Coll Comp Sci & Technol Hangzhou 310027 Peoples R China Washington State Univ Vancouver Sch Engn & Comp Sci Vancouver WA 98686 USA IIT Comp Sci Chicago IL USA

Persistent memory allocation is a fundamental building block for developing high-performance and in- memory applications. Existing persistent memory allocators suffer from many performance issues. First, they may introduce repeated cache line flushes and small random accesses in persistent memory for their poor heap metadata management. Second, they use static slab segregation resulting in a dramatic increase in memory consumption when allocation request size is changed. Third, they are not aware of NUMA effect, leading to remote persistent memory accesses in memory allocation and deallocation processes. In this article, we design a novel allocator, named PMAlloc, to solve the above issues simultaneously. (1) PMAlloc eliminates cache line reflushes by mapping contiguous data blocks in slabs to interleaved metadata entries stored in different cache lines. (2) It writes small metadata units to a persistent bookkeeping log in a sequential pattern to remove random heap metadata accesses in persistent memory. (3) Instead of using static slab segregation, it supports slab morphing, which allows slabs to be transformed between size classes to significantly improve slab usage. (4) It uses a local-first allocation policy to avoid allocating remote memory blocks. And it supports a two-phase deallocation mechanism including recording and synchronization to minimize the number of remote memory access in the deallocation. PMAlloc is complementary to the existing consistency models. Results on six benchmarks demonstrate that PMAlloc improves the performance of state-of-the-art persistent memory allocators by up to 6.4x and 57x for small and large allocations, respectively. PMAlloc with NUMA optimizations brings a 2.9x speedup in multi-socket evaluation and is up to 36x faster than other persistent memory allocators. Using PMAlloc reduces memory usage by up to 57.8%. Besides, we integrate PMAlloc in a persistent FPTree. Compared to the state-of-the-art allocators, PMAlloc improves

关键词： Dynamic memory allocation persistent memory memory fragmentation non-uniform memory access

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The Unexpected Efficiency of Bin Packing Algorithms for Dynamic Storage Allocation in the Wild An Intellectual Abstract 2023

The Unexpected Efficiency of Bin Packing Algorithms for Dyna...

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ACM SIGPLAN International Symposium on memory Management (ISMM)

作者： Lamprakos, Christos Panagiotis Xydis, Sotirios Catthoor, Francky Soudris, Dimitrios Natl Tech Univ Athens Athens Greece Katholieke Univ Leuven Leuven Belgium IMEC Sci Pk Leuven Belgium

ISBN: (纸本)9798400701795

Two-dimensional rectangular bin packing (2DBP) is a known abstraction of dynamic storage allocation (DSA). We argue that such abstractions can aid practical purposes. 2DBP algorithms optimize their placements' makespan, i.e., the size of the used address range. Demand paging-enabled virtual memory systems render makespan irrelevant: allocators commonly employ sparse addressing and need worry only about fragmentation caused within page boundaries. But in the embedded domain, where portions of memory are statically pre-allocated, makespan remains a reasonable metric. Recent work has shown that viewing allocators as blackbox 2DBP solvers bears meaning. There exists a 2DBP-based fragmentation metric which often correlates monotonically with maximum resident set size (RSS). Given the field's indeterminacy with respect to fragmentation definitions, as well as the immense value of physical memory savings, we are motivated to set allocator-generated placements against their 2DBP-devised, makespan-optimizing counterparts. Of course, allocators must operate online while 2DBP algorithms work on complete request traces;but since both sides aim for minimum memory wastage, the idea of studying their relationship preserves its intellectual-and practical-interest. No implementations of 2DBP algorithms for DSA exist. This paper presents a first, though partial, implementation of the state-of-the-art. We validate its functionality by comparing its outputs' makespan to the theoretical upper bound provided by the original authors. Along the way, we identify and document key details to assist analogous future efforts. Our experiments comprise 4 modern allocators and 8 real application workloads. We make several notable observations: in terms of makespan, allocators outperform Robson's worst-case lower bound 93.75% of the time. In 87.5% of cases, GNU's malloc implementation demonstrates equivalent or superior performance to the 2DBP state-of-the-art, despite the second operating offline.

关键词： dynamic storage allocation memory fragmentation bin packing

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Beyond RSS: Towards Intelligent Dynamic memory Management (Work in Progress) 20

Beyond RSS: Towards Intelligent Dynamic Memory Management (W...

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20th ACM SIGPLAN International Conference on Managed Programming Languages and Runtimes (MPLR)

作者： Lamprakos, Christos Panagiotis Xydis, Sotirios Kourzanov, Peter Perumkunnil, Manu Catthoor, Francky Soudris, Dimitrios Natl Tech Univ Athens Athens Greece Katholieke Univ Leuven Leuven Belgium IMEC Leuven Belgium

ISBN: (纸本)9798400703805

The main goal of dynamic memory allocators is to minimize memory fragmentation. fragmentation stems from the interaction between workload behavior and allocator policy. There are, however, no works systematically capturing said interaction. We view this gap as responsible for the absence of a standardized, quantitative fragmentation metric, the lack of workload dynamic memory behavior characterization techniques, and the absence of a standardized benchmark suite targeting dynamic memory allocation. Such shortcomings are profoundly asymmetric to the operation's ubiquity. This paper presents a trace-based simulation methodology for constructing representations of workload-allocator interaction. We use two-dimensional rectangular bin packing (2DBP) as our foundation. 2DBP algorithms minimize their products' makespan, but virtual memory systems employing demand paging deem such a criterion inappropriate. We see an allocator's placement decisions as a solution to a 2DBP instance, optimizing some unknown criterion particular to that allocator's policy. Our end product is a data structure by design concerned with events residing entirely in virtual memory;no information on memory accesses, indexing costs or any other factor is kept. We bootstrap our contribution's utility by exploring its relationship to maximum resident set size (RSS). Our baseline is the assumption that less fragmentation amounts to smaller peak RSS. We thus define a fragmentation metric in the 2DBP substrate and compute it for both single- and multi-threaded workloads linked to 7 modern allocators. We also measure peak RSS for the resulting pairs. Our metric exhibits a monotonic relationship with memory footprint 94% of the time, as inferred via two-tailed statistical hypothesis testing with at least 99% confidence.

关键词： dynamic storage allocation memory fragmentation bin packing

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NVAlloc: Rethinking Heap Metadata Management in Persistent memory Allocators 27

NVAlloc: Rethinking Heap Metadata Management in Persistent M...

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27th ACM International Conference on Architectural Support for Programming Languages and Operating Systems (ASPLOS)

作者： Dang, Zheng He, Shuibing Hong, Peiyi Li, Zhenxin Zhang, Xuechen Sun, Xian-He Chen, Gang Zhejiang Univ Hangzhou Zhejiang Peoples R China Washington State Univ Vancouver WA USA IIT Chicago IL 60616 USA

ISBN: (纸本)9781450392051

Persistent memory allocation is a fundamental building block for developing high-performance and in-memory applications. Existing persistent memory allocators suffer from suboptimal heap organizations that introduce repeated cache line flushes and small random accesses in persistent memory. Worse, many allocators use static slab segregation resulting in a dramatic increase in memory consumption when allocation request size is changed. In this paper, we design a novel allocator, named NVAlloc, to solve the above issues simultaneously. First, NVAlloc eliminates cache line reflushes by mapping contiguous data blocks in slabs to interleaved metadata entries stored in different cache lines. Second, it writes small metadata units to a persistent bookkeeping log in a sequential pattern to remove random heap metadata accesses in persistent memory. Third, instead of using static slab segregation, it supports slab morphing, which allows slabs to be transformed between size classes to significantly improve slab usage. NVAlloc is complementary to the existing consistency models. Results on 6 benchmarks demonstrate that NVAlloc improves the performance of state-of-the-art persistent memory allocators by up to 6.4x and 57x for small and large allocations, respectively. Using NVAlloc reduces memory usage by up to 57.8%. Besides, we integrate NVAlloc in a persistent FPTree. Compared to the state-of-the-art allocators, NVAlloc improves the performance of this application by up to 3.1x.

关键词： dynamic memory allocation persistent memory memory fragmentation

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Are memories of sexual trauma fragmented? A post publication discussion among Richard J. McNally, Dorthe Berntsen, Chris R. Brewin and David C. Rubin

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memory 2022年第5期30卷 658-660页

作者： McNally, Richard J. Berntsen, Dorthe Brewin, Chris R. Rubin, David C. Harvard Univ Dept Psychol 33 Kirkland St Cambridge MA 02138 USA Aarhus Univ Dept Psychol & Behav Sci Aarhus Denmark UCL Clin Educ & Hlth Psychol London England Duke Univ Dept Psychol & Neurosci Durham NC USA

Following the publication of his article on whether memories of trauma in sexual assault victims are fragmented (McNally, 2022), McNally moderated a discussion between Chris R. Brewin and David C. Rubin/Dorthe Berntsen whose perspectives on memory fragmentation were cited by McNally. The discussion clarified their contrasting viewpoints on this controversy.

关键词： memory fragmentation trauma sexual assault

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Are memories of sexual trauma fragmented?

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memory 2022年第1期30卷 26-30页

作者： McNally, Richard J. Harvard Univ Dept Psychol 1230 William James Hall33 Kirkland St Cambridge MA 02138 USA

Alarmingly high rates of sexual assault on campus have motivated American colleges and universities to take steps to address this serious problem. Yet university administrators have often felt ill-equipped to assess allegations of sexual assault. Unsurprisingly, they have sought the expertise of psychologists who can educate administrative staff about the complexities of traumatic memory. Dr. Rebecca Campbell is among the most influential figures teaching university administrators about sexual trauma and memory. The purpose of this article is to review research pertinent to her views on fragmentation of traumatic memories, and the possible roles of tonic immobility and alcohol consumption on how survivors of sexual assault recall their experience.

关键词： Sexual assault trauma memory fragmentation tonic immobility alcohol blackout

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Group system: An efficient dynamic memory management scheme for real-time systems

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JOURNAL OF SYSTEMS ARCHITECTURE 2020年 107卷 101726-101726页

作者： Park, Sung Ho Jeong, Seol Young Kang, Soon Ju Kyungpook Natl Univ Ctr Self Organizing Software Platform 80Daehak Ro Daegu South Korea Kyungpook Natl Univ Coll IT Engn Sch Elect Engn 80Daehak Ro Daegu South Korea

While dynamic memory management (DMM) has been widely used as one of the basic elements of computer systems, it has been rarely used in real-time systems. DMM in real-time systems must exhibit fast execution, high memory efficiency, and predictable execution time. However, it is difficult to design a DMM scheme that simultaneously satisfies all of these requirements, and therefore DMM has not been widely used in real-time systems. This study proposes a new DMM scheme, named group system, that simultaneously satisfies the three requirements of real-time systems. The new DMM scheme is an extension of buddy systems and provides significantly improved memory efficiency compared to buddy systems while maintaining the advantage of the predictable execution time of buddy systems. Group system shows a slightly better worst-case execution time (WCET) than buddy systems that are known to exhibit excellent execution time, and shows memory efficiency that is close to that of the best fit scheme that is known to have excellent memory efficiency.

关键词： Dynamic memory management Heap management Real-time systems Buddy systems memory fragmentation

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